Preparation of highly branched aliphatic hydrocarbons



iinited States Patent PREPARATION OF HIGHLY BRANCHED ALIPHATIC HYDROCARBONS George J. Benoit, In, San Anselmo, Calif., assignor to California Research Corporation, San Francisco, Calif, a corporation of Delaware N0 Drawing. Application December 30, 1954, Serial No. 478,889

6 Claims. (Cl. 260-676) This invention relates to a process for preparing highly branched aliphatic hydrocarbons from lower parafins which comprises heating a lower parafiin or mixture of lower paraftins in the presence of a lower dialkyl peroxide, alkyl hydroperoxide or diacyl .peroxide. In particular, this invention relates to a process for preparing highly ranched aliphatic hydrocarbons which comprises heating a lower paraffin or mixture of lower parafiins and propane in the presence of a lower dialkyl peroxide.

Highly branched aliphatic hydrocarbons are used extensively in the production of hydrocarbon motor fuels. It is well known that the knocking characteristics of hydro carbon motor fuels represent a dissipation of considerable energy, and in view of the modern trend toward more etlicient, higher compression engines, it becomes extremely important to minimize such knocking. It has been found that this dissipation of energy is most serious in the case of straight-chain aliphatic hydrocarbons and becomes progressively less severe with branched or unsaturated hydrocarbons, cyclic paraflins and aromatic hydrocarbons. Inasmuch as straight-chain aliphatic hydrocarbons make up the bulk of hydrocarbons available for use as motor fuels, it is customary to blend them with those hydrohydrocarbons are especially valuable for this purpose since not only do they have a high octane value, but also they are compatible with tetraethyl lead which is also added to produce high octane fuels. However, since the amount of high octane blending stocks is relatively limited, it would be desirable if a method were available for converting the less attractive, essentially straightchain materials to those of a branched character, and it is, therefore, an object of this invention to provide such a method.

The present invention is based on the discovery that the foregoing object can be achieved, with highly branched aliphatic hydrocarbons being produced from lower parafliuic hydrocarbons, by a process wherein a lower paraffin or a mixture of such parafiins is heated in the presence of a peroxide to a temperature affording decomposition of the peroxide at a reasonable rate, said temperatures normally being in the range of from about 150-400" F. depending on the particular peroxide employed. The reaction can be conducted at either atmospheric or superatmospheric conditions, and is preferably efiected by continuously agitating the reaction mixture for a period of from about 2 to 60 hours. The relative amount of peroxide initiator to hydrocarbon reactant employed can be varied from about 0.02 to 0.5 mole of peroxide for each mole of the parafiinic reactant, though the reaction of the present invention will go forward in limited degree even outside these limits. A preferred range is from about 0.05 to 0.2 mole of the peroxide per mole of the lower parafiin or paraflins.

As the hydrocarbon reactant there can be employed any one or more of the lower paraffin compounds conice taining from about 3 to 5 carbon atoms per molecule, not more than one of which carbon atoms is in a branched position. Representative reactants of this character include propane, n-butane, isobutane, n-pentane and Z-methyl butane. Particularly good results have been obtained when propane is employed either alone or in admixture with isobutane.

As the peroxide material, there can be employed a dialkyl peroxide, an alkyl hydroperoxide, a diacyl peroxide, or mixture of such peroxides. Preferably, however, the peroxide employed is one of the dialkyl variety such, for example, as di-(tert.-butyl) peroxide, methyl ethyl peroxide, di-(sec.-butyl) peroxide, or the like, though di-(tert.-butyl) peroxide is preferred since it has the advantage of commercial availability and is also relatively stable. It has been observed that the highest conversions are obtained with the use of a dialkyl peroxide, with somewhat lower conversions being obtained with alkyl hydroperoxides (e. g., tert.-butyl hydroperoxide), and with still smaller conversions being obtained with acyl peroxides (e. g., benzoyl peroxide and lauroyl peroxide).

As regards the nature of the product produced by a practice of the present invention, the term highly branched aliphatic hydrocarbon is employed herein and in the appended claims to describe said products, said term indicating parafinic hydrocarbons which contain at least 5 and preferably 6 or more carbon atoms in the molecule, with at least 2 of said carbon atoms being in a branched position.

The invention is illustrated in various of its embodiments by the following examples.

Example I 100 grams of di-(tert.-butyl) peroxide were placed in a stainless steel bomb equipped with a heater and means of agitation. The bomb was repeatedly flushed with nitrogen to replace air. isobutane (300 grams) and propane (300 grams) were then pumped into the bomb. The bomb was heated to 300 F. at a pressure of 1100 p. s. i. g. and held at that temperature for 12 hours, following which it was cooled to room temperature. Gas was bled off into a gas holder; a total of 237 liters at 55 F. was collected. The gas was found to be largely isobutane and propane with smaller amounts of hydrogen, methane, ethane, ethylene, propene, butene and C5 hydrocarbons also present. Of the propane charged, 73% was recovered; of the isobutane charged was recovered.

The bomb liquid product amounted to 146 grams. It was water-washed repeatedly. The oil phase from the washing was dried over K2003. The dried material (33 grams) was distilled through an 18-inch zigzag column, using a 9:1 reflux ratio. 16 grams of highly branched hydrocarbons were obtained within the boiling point range, 154223 F. (Cs to C8). Of this amount, six grams were triptane (2,2,3-trimethylbutane).

Example 11 Following the procedure of Example I, from 300 parts by weight of isobutane, 300 parts by weight of propane and parts by weight of di-(tert.-butyl) peroxide heated at a temperature of 266 F. and a pressure of about 900 p. s. i. for 54 hours were produced 9 grams of highly branched C5 to Ca paraflins, including 6 grams of triptane.

Example III Following the procedure of Example I, from 300 parts by weight of isobutane, 300 parts by weight of propane and 100 parts by weight of di-(tcrt.-butyl) peroxide heated at a temperature of 347 F. and a pressure of 1400 p. s. i. g. for 12 hours were produced 13.9 grams 3 of highly branched C6 to Ca parafiins, including 6.1 grams of triptane.

Example IV Following the procedure of Example III, substituting an equimolar amount of di-(tert-amyl) peroxide for di-(tert.-butyl) peroxide, essentially the same amount of branched paraflins was obtained.

Example V Following the procedure of Example I, from 300 parts by weight of isobutane, 300 parts by weight of propane and 100 parts by weight of tert.-butyl hydroperoxide heated at a temperature of 320 F. and a pressure of 1100 p. s. i. g. for 12 hours were produced 0.4 gram of highly branched parafiins.

Example VII Following the procedure of Example I, from 300 parts by weight of isobutane, 300 parts by weight of propane and 100 parts by weight of benzoyl peroxide heated at a temperature of 212 F. and a pressure of 500 p. s. i. g. for 48 hours were produced about 0.4 gram of C6 to C7 branched parafiin hydrocarbons.

Example VIII Following the procedure of Example I, from 180 parts by weight of isobutane, 180 parts by weight of propane and 100 parts by weight of lauroyl peroxide heated at a temperature of 212 F. and a pressure of 575 p. s. i. g. for 24 hours were produced only traces of Cs+ branched hydrocarbons.

Example IX Following the procedure of Example I, omitting the inclusion of any di-(tert.-butyl) peroxide, only traces of a liquid product were obtained.

Example X Following the procedure of Example I, omitting both isobutane and propane, only traces of a liquid product were observed.

Iclaim:

1. A process for preparing highly branched aliphatic hydrocarbons which comprises heating a lower parafl'in in the presence of at least one peroxide selected from the group consisting of dialkyl peroxides, alkyl hydroperoxides and acyl peroxides, said heating being at a temperature between about and 400 F., sufficient to effect decomposition of the peroxide.

2. A process for preparing highly branched aliphatic hydrocarbons which comprises heating a mixture of lower paraflins in the presence of a dialkyl peroxide, saidheating being at a temperature between about 150 and 400 F., sufficient to effect decomposition of the peroxide.

3. A process for preparing highly branched aliphatic hydrocarbons which comprises heating a lower paraflin and propane in the presence of a lower dialkyl peroxide, said heating being at a temperature between about 150 and 400 F., sufficient to effect decomposition of the peroxide.

4. A process for preparing highly branched aliphatic hydrocarbons which comprises heating at least one lower parafiln in the presence of from 0.02 to 0.5 mole of a peroxide per mole of lower parafiin, said heating being at a temperature between about 150 and 400 F., sufficient to effect decomposition of the peroxide.

5. A process for preparing highly branched aliphatic hydrocarbons which comprises heating a mixture of lower paraifins in the presence of from 0.02 to 0.5 mole of at least one dialkyl peroxide per mole of said parafiin mixture, said heating being at a temperature between about 150 and 400 F., sufficient to elfect decomposition of the peroxide.

6. A process for preparing highly branched aliphatic hydrocarbons which comprises heating a mixture of propane and isobutane in the presence of from 0.02 to 0.5 mole of di-(tert.-butyl) peroxide per mole of said mixture, said heating being at a temperature between about 150 and 400 F., sufiicient to effect decomposition of the peroxide.

References Cited in the file of this patent UNITED STATES PATENTS 2,270,669 De Sirno et al Jan. 20, 1942 2,306,253 McMillan Dec. 22, 1942 2,385,344 Burk Sept. 25, 1945 2,530,874 Gwynn et al. Nov. 21, 1950 

1. A PROCESS FOR PREPARING HIGHLY BRANCHED ALIPHATIC HYDROCARBONS WHICH COMPRISES HEATING A LOWER PARAFFIN IN THE PRESENCE OF AT LEAST ONE PEROXIDE SELECTED FROM THE GROUP CONSISTING OF DIALKYL PEROXIDES, ALKYL HYDROPEROXIDES AND ACYL PEROXIDES, SAID HEATING BEING AT A TEMPERATURE BETWEEN ABOUT 150 AND 400* F., SUFFICIENT TO EFFECT DECOMPOSITION OF THE PEROXIDE. 